Lithium DoD Claims and End of Life Capacity statements are Inconsistent

richardimorserichardimorse Registered Users Posts: 90 ✭✭
If at End of life you have a Lithium battery with 60% of its original capacity
e.g. 40,000 Wh New = 24,000 Wh End of Life
How can you claim to be able to go to 70% Depth of Discharge thought the battery life ?
You can start with 70% of 40,000 = 28,000 Wh Usable and end with 70% of 24,000 = 16,800 Wh usable

So unless you reduce power consumption over the 10 year lifetime = Is not going to happen  = power consumption always goes up
At some point in the battery lifetime it stops becoming usable for the purpose intended, i.e. you can't get 28,000 Wh out of 24,000 Wh

So what is the impact of this on battery life, in my opinion it makes a mockery of battery life claims to have a caveat that says provided you keep reducing power consumption to fit battery bank capacity and hence ensure you do not exceed 70% DoD that the battery will last 10 years

So what about battery bank sizing should we be sizing for something in the middle, at least if you size for 60% DoD on Lithium, there is still 60% capacity left at end of life so you don't have to go over 100% DoD to get your power budget from the battery

This tells me the basis of battery bank life claims is fraudulent and do not reflect reality, how can I have a 10 year life at 70% DoD if there is only 60% capacity left after 10 years = Only by reducing power consumption over the 10 years, hence how can someone size a lithium battery bank for 70% DoD when there is going to be a 10% deficit at end of life. . .

The same may be true for Lead Acid but at least they only go down to 80% capacity at end of life and not 60% of installed capacity like Lithium, so should we be sizing on the mid point, i.e. 90% capacity for Lead Acid and 80% capacity for Lithium or to put it another way, take 10% off all DoD claims for any battery and use that for sizing purposes, e.g. if Lithium says 10 years at 70% DoD then read that as 10 Years at 60% DoD

Comments

  • mike95490mike95490 Solar Expert Posts: 8,468 ✭✭✭✭✭
    Yep.  At some point, Li based batteries give out, either worn out, or calendar lifetime takes it toll.  I can't figure out, laptop and cell phone batteries, when well used, last 3 years or so and there's been tons of work to keep them going.  I think folks have banks that are ramping down in capacity, and some day they will wake up in a dark house.   There's been no breakthrough in Li tech, so there is no amazing increase in life except for oversizing the bank initially
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
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  • richardimorserichardimorse Registered Users Posts: 90 ✭✭
    Here is a profile for Lead Carbon Batteries

    The above takes a 2400Ah 48V Battery bank = 115,200 Wh as an example, you can get away with the 8% drop in DoD on the basis of oversizing which is what we have all been doing for years, i.e. start off at 26% DoD and end up with 34% DoD and things should average out, we used a 1.5 power conversion multiplier when working out the power budget of 36,000 so plenty of headroom.

    Here is a profile for Lithium batteries


    Here the advertised 10 year life at 70% DoD is not possible to achieve, because the end of life capacity is 60%, so all you people out there sizing Lithium batteries at 70% DoD better head for the hills when you customer comes back in 7 years with a broken battery bank, I know what the battery manufacturers will say and it is something like

    "You get a 10 year life if you maintain a 70% DoD that means if the battery bank capacity reduces by 20% after 5 years then the amount of power you take from the battery must also reduce by 20% in order to remain at a 70% DoD and get a 10 year lifetime"

    The problem is that the customer power draw does not go down, so you should NEVER size Lithium batteries at 70% DoD of the starting battery life and should start with Worst case 60% DoD, that way at end of life you are only running at 100% DoD instead of 113%

  • mcgivormcgivor Solar Expert Posts: 3,161 ✭✭✭✭✭
    Sizing a bank based on maximum daily discharge with any chemistry is not a wise choice, although LFP can be deeply cycled, a more conservative approach is the better choice, which is why many consider with days of autonomy. The benefits of having a larger capacity will be the reduced depth of discharge, an occasional deep discharge will not have a significant effect on capacity over time. The most important advantage is, LFP can tolerate being in a partial state of charge, something LA (lead carbon) for example do not. So with the charts, what would be the comparison look like if the DOD were both 30%? 19 years life expectancy on lead carbon is probably very optimistic, which makes me wonder what the source of the charts is, a lead carbon battery manufacturer perhaps?  Then there are details,  what temperature is the projected life expectancy calculated at? There are manufacturers of tubular LA cells which claim 9000 cycles, but the small print states at a temperature of 20°C.

    Naturally lithium battery manufacturers will have similar  charts which work in their favour, I'm not attempting to argue by any means, but lead carbon are still lead acid, the negative plate is a lead carbon composite which is supposed to "potentially reduces sulfation, reduce positive plate corrosion " though never eliminates these traits, alloys of lead anttomony and selenium were also used as an attempt  to improve a technology which is fast approaching it's end of life. Just an option.


    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • richardimorserichardimorse Registered Users Posts: 90 ✭✭
    edited January 17 #5
    Both Lead Carbon and Lithium are designed for PSOC operations and both can tolerate being in a partial state of charge, LA can not but LC and LFP are both designed for PSOC operations, here is some literature explaining the PSOC operation of Lead Carbon.

    http://www.trojanbattery.com/wp-content/uploads/2014/01/SmartCarbon_Overview.pdf
    https://www.industrie-techno.com/mediatheque/2/1/6/000011612.pdf
    https://www.solarwirtschaft.de/fileadmin/media/pdf/offgrid_2015/Advanced-Lead-Acid-Batteries.pdf
    https://northstarbatteries.azurewebsites.net/genset-solutions
    https://www.hotspotenergy.com/solar-batteries/REXC-Series-Operation-Manual.pdf
    https://prod-ng.sandia.gov/techlib-noauth/access-control.cgi/2009/095537.pdf
    https://asianbatteryconference.com/wp-content/uploads/sites/59/2017/10/Jiayuan_Xiang-1.pdf

    LFC has a single advantage, which is actually several in one, that is that it isolates failed batteries and continues to operate and that at end of life it remains usable, however defining end of life is the issue and many LFP proponents define it incorrectly as my sizing comparison shows.

    I have not come across anyone over configuring LFP people are putting in undersized solutions due to client budget restraints with a promise to add a 3rd battery when the client can afford it within the next 3 years, when clearly the battery bank can NEVER be proposed at 70% DoD or at 60% DoD as part of daily cycle operations and that a 50% DoD should be the maximum proposed.

    LFP at 60% DoD claims a 15 year battery life but that is untrue in that it ends up with a 100% DoD at end of life, and hence would be withdrawn from service after 10 years to avoid trashing the battery (if someone is still monitoring it after 10 years) and redeployed, the advantage of LFP is that the remaining 60% capacity can be re-used for a second period of 10 years but for a different site or application which requires 40% less power than the site the battery bank is being decommissioned from.

    Hence my point is that LFP can not achieve the stated lifetime in daily cycle operations and can not be operated at 70% DoD for 10 years
    The LFP battery manufacturers quote these figures for daily cycle operations and not for occasional deep discharge use.

    Quoting a 60% DoD for a 15 year lifetime resulting in 60% capacity left in the battery is simply UNTRUE and not achievable.
    If you were to use a 60% DoD you would have to withdraw the battery from service after 10 years with 75% capacity left in the battery.

    As for LC it is also a new technology but promises PSOC operation like LFP as can be seen from the literature.
  • mcgivormcgivor Solar Expert Posts: 3,161 ✭✭✭✭✭
    LC is NOT a new technology it's like adding raisns to bread to get rasin bread, perhaps it enhances the bread, but it remains bread. Let me guess, you have the new enhanced lead acid batteries and are attempting to prove a point, again not provoking an argument.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • mcgivormcgivor Solar Expert Posts: 3,161 ✭✭✭✭✭
    edited January 17 #7
    What temperatures are these numbers related to? Just curious.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • richardimorserichardimorse Registered Users Posts: 90 ✭✭
    edited January 19 #8

    Carbon AGM battery technology and Lithium battery technology both decrease capacity at low temperatures to the same extent, at 0°C both technologies decrease capacity by only 10% and not the 33% that would occur with Flooded Lead Acid technology at 0°C.

    Carbon AGM battery capacity increases at high temperatures, at 35°C the capacity increases by 5% and sulphation decreases, the required floating and equalisation voltages are lower at higher temperatures, which results in a slow down in corruption of the grids

    The down side of higher temperatures is that plate corrosion and water loss is accelerated, at 35°C battery life is halved to 10 years, at 28°C it is reduced to 16 years, that figure is for an average of 28°C for the entire year not a 2 month average temperature.  

    You also have to factor into the calculation the time to warm up from 20 hours of lower temperatures compared to the time to cool down from 4 hour maximum temperatures which can be a significant factor for cold climates when it never appears to warm up in the day.

    My installation has a 20°C-27°C average temperature, the optimum operating temperature range of Carbon AGM is 15°C to 25°C 

    I am not sure if there is a problem with Carbon AGM technology in colder climates due to both battery technologies having 10% less capacity at 0°C, but their is for hotter climates which may require DC powered cooling systems to prevent battery dry out.

  • EstragonEstragon Registered Users Posts: 4,179 ✭✭✭✭✭
    Hate to pick pits, but LA would be 50% of nameplate capacity at ~0°F or -18°C.  At 0°C, it would be on the order of 2/3. 

    Doesn't really matter in your application, just pointing it out for anyone it might..
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • karrakkarrak Solar Expert Posts: 326 ✭✭✭✭
    If at End of life you have a Lithium battery with 60% of its original capacity
    e.g. 40,000 Wh New = 24,000 Wh End of Life
    How can you claim to be able to go to 70% Depth of Discharge thought the battery life ?
    You can start with 70% of 40,000 = 28,000 Wh Usable and end with 70% of 24,000 = 16,800 Wh usable
    Can you provide a link to the source of this information?

    The same may be true for Lead Acid but at least they only go down to 80% capacity at end of life and not 60% of installed capacity like Lithium, so should we be sizing on the mid point, i.e. 90% capacity for Lead Acid and 80% capacity for Lithium or to put it another way, take 10% off all DoD claims for any battery and use that for sizing purposes, e.g. if Lithium says 10 years at 70% DoD then read that as 10 Years at 60% DoD
    Lets compare like with like. If we are cycling 70% of SOC from Trojan's own information we only get ~2500 cycles or around 6.8 years from their best batteries before they are toast whereas after 6.8 years from your figures with LFP batteries we still have ~73% of capacity and a perfectly usable battery.
    It is not reduction in capacity that kills lead acid batteries. By the time the capacity of a LA battery has dropped to 80% the  internal resistance has increased and the charging efficiency has decreased so much that the battery becomes unusable.

    This is not the case with LFP batteries. The internal resistance and the charge efficiency does not change significantly over time. The only thing that changes significantly is the capacity. This means that the battery still remains usable but with a reducing capacity over its lifetime.

    The decrease in charging efficiency and increase in internal resistance makes it unwise to add new cells to a lead acid battery at a later date as the new cells end up being overcharged and the old cells don't get fully charged. This is not the case with LFP batteries. If you require an increase in capacity at a later date just add more cells.

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
    modified BMS based on TI bq769x0 cell monitors.
    Homemade overall system monitoring and power management  https://github.com/simat/BatteryMonitor
     

  • richardimorserichardimorse Registered Users Posts: 90 ✭✭
    LFP manufacturers state not to add new LFP with old LFP after 3 years, what you can do is factory refurbish the LFP, then you can do this, or just sell it for its residual asset value and buy new
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,840 ✭✭✭✭✭
    LFP manufacturers state not to add new LFP with old LFP after 3 years, what you can do is factory refurbish the LFP, then you can do this, or just sell it for its residual asset value and buy new
    Context here is not correct for me at least. The LFP battery systems I use can be added any time as they are a standalone battery system with internal BMS and data out by canbus.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
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  • AmpsterAmpster Registered Users Posts: 132 ✭✭✭
    edited February 11 #13
    LFP manufacturers state not to add new LFP with old LFP after 3 years, what you can do is factory refurbish the LFP, then you can do this, or just sell it for its residual asset value and buy new
    Factory refurbish? Show me which manufacturers do this. I trust that @Karrak has the science correct as far as mixing old LFP with new in parallel strings. I would want to watch for voltage imbalances if I were replacing a cell in a string of series single cells.
  • karrakkarrak Solar Expert Posts: 326 ✭✭✭✭

    LFP manufacturers state not to add new LFP with old LFP after 3 years, what you can do is factory refurbish the LFP, then you can do this, or just sell it for its residual asset value and buy new
    Can you provide links to manufactures that say this?

    I would be interested to know the technical reasons why you disagree with my last post

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
    modified BMS based on TI bq769x0 cell monitors.
    Homemade overall system monitoring and power management  https://github.com/simat/BatteryMonitor
     

  • karrakkarrak Solar Expert Posts: 326 ✭✭✭✭
    Ampster said:
    Factory refurbish? Show me which manufacturers do this. I trust that @Karrak has the science correct as far as mixing old LFP with new in parallel strings. I would want to watch for voltage imbalances if I were replacing a cell in a string of series single cells.
    You could run into balance problems if you were only replacing one cell. If you were to add to an existing battery I would parallel up the new cells with all the existing series cells.

    Lets say you started with a 100Ah 2p16s battery that had lost 30% of its capacity over time and you wanted to increase the capacity of the battery. You would purchase 16 new 50Ah cells and add them to the existing battery to make it a 3p16s battery with a new capacity of 120Ah.

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
    modified BMS based on TI bq769x0 cell monitors.
    Homemade overall system monitoring and power management  https://github.com/simat/BatteryMonitor
     

  • jonrjonr Solar Expert Posts: 1,326 ✭✭✭✭
    As Karrak says, as the lithium bank ages, you add more parallel capacity.    So it is reasonable to start out with a lithium bank sized for 70% DOD.

    I am available for custom hardware/firmware development

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